There are no direct methods in the Extensions API for write-back. Write-back is something that you can now do directly in your dashboard with the Extensions API because you can retrieve data with the API and send it to your database (i.e. with a server endpoint).

I need to start build the writeback api extension to make use of my one of the Tableau project. I am getting confused where to get start. Can you help me to build the writeback extension to my project.?

Take a look at this simple example from one of my coworkers showing how you can write back to an excel file. You should be able to pull the pieces you need and adjust to match your data source! GitHub - Kovner/InventoryManagement

I have one more quick question. Do we really need a Tableau version(2018.2 or higher) with the end users to update the values in the report or they should be fine to update values in the front end portal, where we have our tableau dashboard published.?

We have a dashboard, where we have 3 specific charts related to our project, we would want to restrict the users for write back functionality on specific charts. Can we achieve this by using Write Back extension.

Do we need to set any specific permissions to update each charts, if so how can we make within that Tableau Dashboard?

I am able to write back to the excel spreadsheet by using write back extension within the Tableau session, I would want the end user should be update the published Tableau dashboard through server by using this write back extension. We are using Tableau 2018.2. Please share if you've any insights.

If you want this ability on Server, your extension will need to have access to the data source you want to write back to, e.g a SQL database. As far as controlling the write back for specific charts, yes you can definitely do this, it will depend on how you write the extension.